The invention is directed to a spindle drive with a spindle and a spindle nut running thereon for the high-precision drive of a linearly movable device.
Spindle drives are employed, for example, in electronic reproduction technology in electronic recording devices for the point-by-point and line-by-line exposing of recording materials, also referred to as output scanners, exposers or recorders.
In an electronic recording device of the flatbed type, the recording material to be exposed is chucked on a linearly movable table or carriage, and the recording element is stationarily arranged. Given a recording device of the inside-drum type, recording material is located in a stationary, cylindrical segment-like holder, and the recording element is mounted on a linearly movable table or carriage. The table or carriage is mechanically rigidly connected to a spindle nut with which the rotary motion of a spindle driven by a motor is converted into a linear motion of the table or carriage.
Required, among other things, in order to achieve a good recording quality, particularly in the rastered exposure of recording materials, is a uniform linear speed of the table or the carriage that is essentially dependent on the quality of the spindle drive. Given recording devices that work in a start/stop mode, the spindle drive must--beyond this--enable a high precision in the positioning of the table or carriage along the spindle. The synchronism and positioning precision should thereby be assured in both directions of the linear motion.
CH-A-344 87 already discloses a two-part spindle nut for a spindle. The spindle nut is composed of two slide nut segments that are guided by a guide member movable in the radial direction relative to the spindle and in anti-tilt fashion.
A uniform linear motion and a high positioning precision cannot be assured in all instances with the known two-part spindle nut. There is the conflict in goal between a spindle nut lying as closely as possible against the spindle that, however, tends to seize at the spindle, and an easily movable spindle nut with an associated slack that disadvantageously deteriorates the uniformity of the linear motion and the positioning precision.
U.S. Pat. No. 2,493,000 discloses that axial sidewall play between slide nut segments and a spindle be eliminated with a spring. The elimination of the sidewall play, however, does not occur dependent on the selectable direction of a linear motion of an element driven by the spindle.